A large industry has grown up around the need for thermal plastic sheet materials used as a barrier against the heat of sunlight incident upon windows and glass walls in buildings. The soaring cost of energy coupled with the ever growing glass areas in contemporary buildings has generated a strong demand for window coverings and especially for transparent films which block the infrared energy of sunlight.
Thermal rejection films consist of one or more layers of transparent plastic film having colorations through tinting, metallization or other means. The film is bonded to the interior of window glass using adhesive agents. The practise has become wide spread and is used now for automobile windows as well as for buildings. For buildings with glass windows or walls which are not otherwise treated to reject thermal energy, it has been found that installation of such films quickly pays for itself by lowering air conditioning expense in the summer and heating costs in winter. Additionally, those who sit at or near windows find it more comfortable when the glass is so insulated.
The installation method includes cleaning of the interior of the window glass, wetting the glass, cutting the film to appropriate width, cutting the film to appropriate lengths, stripping a protective layer from the tinted film, laying the film against the moistened window glass, and applying pressure to squeeze out both moisture and air allowing the film to make intimate contact with the glass. Quality film stock has a scratch resistant coating on the outside so that the installation is more or less permanent. Because the cost of installation is a significant factor in determining the practicality of its use, improvements to film quality and reduction of installation costs are of importance.
There are a large number of machine designs in use for the shearing or cutting and dispensing of rolled goods. Examples include U.S. Pat. No. 3,786,705 to Dorfel which teaches a means for slitting a web longitudinally into at least two narrower webs, U.S. Pat. No. 3,760,669 to Rosenthal and Matsouka, and also U.S. Pat. No. 3,788,175 to Davis which teaches several means for unwinding and laterally cutting off measured lengths of a stock roll, and U.S. Pat. No. 3,967,519 to Esterly which teaches the multidirectional cutting of a web. These machines are large, heavy and not suitable for use in the field.
The prior art does not disclose a means for measuring and slitting window film to width, measuring and cutting it to length, indicating length of film left on the supply roll, and dispensing said precut pieces with backing film automatically removed; ready for installation. There is a particular absence of prior art teaching of portable equipment intended for the above purpose. It is the applicant's opinion that the present invention is new in these and other respects to be shown herein.